Helmet for displaying environmental images in critical environments

ABSTRACT

A helmet for displaying environmental images in critical environments, comprising at least one video camera and a display for displaying environmental images; the helmet also has a supporting structure that can be anchored to the helmet in order to support the at least one video camera and the display; the supporting structure has a front adapter that can be coupled to a front edge of the helmet, a rear adapter that can be coupled to a rear edge of the helmet, and a connecting element for mutually connecting the front adapter and the rear adapter.

TECHNICAL FIELD

The present invention relates to a helmet for displaying environmentalimages in critical environments, particularly areas at risk of accidentor in which an accident has occurred such as tunnels, subways, woodedareas, refineries, nuclear facilities, shopping centers and in generalsites with high concentrations of people.

BACKGROUND ART

In these critical areas, actions for intervention and rescue on the partof firefighters or law enforcement personnel in case of an accident areparticularly risky for the injured people, for their rescuers and forall the people involved in the accident, since the escape routes areoften difficult to detect. The smoke of a fire, darkness or fog are thefactors that most significantly compromise the effectiveness andswiftness of an intervention.

These factors can themselves be the cause of an accident or can worsenone, since even in the absence of an accident, in certain critical areas(such as for example tunnels) it is necessary to ensure safety bypreventing accidents caused by particular environmental conditions.

Systems are currently known which send images from fixed stations to acontrol center, which coordinates operations by radio.

Portable or helmet-mounted mobile systems that improve the vision of theindividual user are also known. In particular, U.S. Pat. No. 6,255,650in the name of Flir Systems, Inc. describes a system that is formed byan infrared (IR) television camera, a display, electronic and powersupply circuits which are integrated in a portable, stand-aloneapparatus that is shaped so as to be worn on one's head; this televisioncamera-display system improves vision in environments with denseparticulate, with extreme temperatures such as those that occur infires. Vision can be monoscopic or stereoscopic and is enhanced bycolor-coding the temperature, by means of a processor and by way ofreflective and opaque lenses arranged approximately at eye level inorder to produce bright and sharp images.

Optionally, the system comprises an external video recorder andtransmitter; the video transmitter also transmits radiometric data.

U.S. Pat. No. 5,200,827 describes another video camera-display systemthat is conceived to be mounted on the helmet of a soldier. The systemallows to display at close range pictures that originate from a remotelocation and is used for example to transmit pictures from the combatarea toward the rearguard.

Transmission between the video camera (mounted on a rifle or hinged onthe helmet) and the display (mounted on the helmet) occurs by means ofan electric wire, optical fiber or wirelessly, and a transmitter allowsmultiple individuals to view the picture that arrives from a singlevideo camera; each one of the involved individuals can select thepicture generated by several remote video cameras.

The display used in U.S. Pat. No. 5,200,827 is transparent in order toallow the user to view the environment; in particular, the picture isobtained by means of a holographic projection on a clear peak. Moreover,the display operates with an image separator arranged on the line ofsight of the person in order to allow to view a superimposed scene ofthe object on the line of sight and on the display.

Finally, patent FR 2602347 describes an apparatus that is constituted byan infrared sensor, a laser rangefinder and a device for alignment withthe rangefinder. The apparatus operates on two optical communicationpathways that work in different spectral domains.

Known systems and devices are limited in monitoring and rescueapplications in critical areas because they do not integrate informationeffectively. In particular, fixed-station systems require a controlcenter that coordinates operations by radio, and this control centerdoes not retransmit received pictures or any real-time processing ofsaid pictures.

Furthermore, the pictures displayed on the display originate from asingle video camera and interaction with other video cameras occursaccording to a direct link.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to overcome the limitationsdescribed above by providing a helmet for surveillance of critical areasthat is of the modular type and in which the components can be insertedin an integrated system that allows users to share a greater amount ofinformation.

Within this aim, an object of the invention is to increase interventionefficiency in case of accident and to reduce the risks linked to saidintervention operations.

Another object is to improve the quality of the picture displayed by theuser in order to make the monitored situation more comprehensible.

Another object is to provide an anchoring system that is flexible andinexpensive, allowing use on existing helmets.

This aim and these and other objects that will become better apparenthereinafter are achieved by the helmet for displaying environmentalimages in critical environments according to the present invention,which comprises at least one video camera and means for displayingenvironmental images, characterized in that it comprises a supportingstructure that can be anchored to said helmet in order to support saidat least one video camera and said display means, said supportingstructure comprising a front adapter that can be coupled to a front edgeof said helmet, a rear adapter that can be coupled to a rear edge ofsaid helmet, and a connecting element for mutually connecting said frontadapter and said rear adapter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the description of a preferred but not exclusiveembodiment of the modular surveillance system, illustrated by way ofnonlimiting example in the accompanying drawings, wherein:

FIG. 1 is a block diagram of a surveillance system for application tothe invention;

FIG. 2 a is a simplified block diagram of the electronic circuit forprocessing the signals acquired in a mobile station;

FIG. 2 b is a simplified block diagram of the electronic circuit forprocessing the signals acquired in a fixed station;

FIG. 3 a is an exploded view of the block diagram of the electroniccircuit of FIG. 2 a;

FIG. 3 b is a view of a structure for mutually connecting the variousstations of a surveillance system;

FIG. 4 a is a perspective view of the arrangement of video cameras thatoperate in different spectral regimes;

FIG. 4 b is a view of an example of a common reference for calibratingthe proportionality coefficients to be applied to the various videocameras by means of the magnification coefficient of the optical systemsarranged in front of them, in order to have a perfect match of theimages in the various spectral domains with a 1:1 scale ratio;

FIG. 5 a is a schematic map view of the arrangement of the componentslocated upstream of a video camera or optionally of a combination ofmutually coupled video cameras;

FIG. 5 b is a schematic map view of the arrangement of the componentsupstream of a video camera or optionally of a combination of mutuallycoupled video cameras;

FIG. 5 c is a schematic side view of the structure for displayingstereoscopic images, with additional details;

FIG. 5 d is a view of the viewing field obtained by means of therotation of a mirror arranged on a galvanometer motor, taking intoaccount the visual cone of the video camera and allowing to make remarksregarding the minimum dimensions of the optical systems and theirlocation;

FIG. 6 a is a view of a particular arrangement of the components of ahelmet-mounted mobile station according to the invention;

FIG. 6 b is a view of a particular arrangement of the components of avehicle-mounted mobile station;

FIG. 6 c is a view of a particular arrangement of the components of aportable mobile station;

FIG. 6 d is a view of a device for anchoring on a helmet according to aparticular aspect of the invention;

FIG. 6 e is a view of a detail of the structure for supporting thedisplays to be mounted on the helmet according to the invention;

FIG. 6 f is a front view of a helmet adaptor according to a particularaspect of the invention;

FIG. 7 is a view of a particular arrangement of the components of afixed station;

FIG. 8 is a more detailed diagram of the channels for communicationbetween fixed stations and mobile stations;

FIG. 9 is a view of an application of the surveillance system inautomotive applications.

WAYS TO CARRYING OUT THE INVENTION

With reference to FIG. 1, the surveillance system comprises a number offixed stations 10 a-101 and a number of mobile stations 12 a-12 e.

The fixed stations are inserted in a network, preferably of thefiber-optic type with known layouts such as a ring 11 or a star 13 orlinear layouts, and are mutually connected according to a cluster-typelayout, in which combinations of the layouts 11 and 13 and linearlayouts are repeated according to the surveillance requirements to bemet.

Said fiber-optic system can be connected to a control center 14, whichhas processing and supervision functions, and to a mobile processingcenter 15, which is typically mounted on a vehicle. Each station cancommunicate bidirectionally with any other fixed or mobile station.

The mobile stations are of different types, and as will become betterapparent hereinafter, they can be mounted on a helmet, on vehicles suchas cars, trucks, aircraft, on autonomous self-propelled robots, or onhandheld portable systems.

In FIG. 1, each station has been shown schematically as beingconstituted by a video block (VIDEO) and a communication block (TX/RX).

The distinction into two blocks is purely an example; actually, everystation is built according to a modular structure, in which the variouscomponents are removable and interchangeable in their arrangement,depending on the particular type of station in which they are mounted.

The video block (VIDEO) comprises the components required foracquisition, processing and display of the environmental images.

The communications block (TX/RX) instead comprises the means forcommunicating the acquired environmental images that are needed in orderto receive and transmit environmental images (encoded into video signalsaccording to known methods); each mobile station is a terminal thatsimultaneously receives and transmits video images from and toward otherstations of the network.

In greater detail, each mobile station comprises at least one videocamera for acquiring environmental images and at least one display toallow the viewing of said images by a user; each fixed station alsocomprises at least one video camera and optionally a display, which isnot necessarily mounted in the same location as the station.

Preferably, the stations further comprise a number of additional videocameras that are coupled to said at least one video camera for theacquisition, along a same optical axis, of images of a same environmentin different spectral domains, according to the arrangement and theconnections described in greater detail hereinafter.

The mobile processing center and the control center comprise at leastone display for displaying the video signals of the network andoptionally one or more video cameras.

The displays can be of a common type, or, as described hereinafter, of amore specific type, depending on the applications.

Multiple video cameras can be mounted in the individual station; apreferred embodiment uses at least one video camera of the thermographictype, which operates in the infrared spectral range (in order to detectwavelengths between approximately 2 and 14 μm), and at least one secondvideo camera, which operates in a spectral domain that is different fromthe infrared (for example, in the visible-light range between 400 and700 nm or as an alternative in the near infrared from 700 to 1900 nm).

Preferably, each station uses two video signals that are either of thethermographic type, i.e., characterized by radiation that originatesfrom the emission of the observed bodies themselves (any body emits heatradiation merely due to the fact that its temperature is higher thanabsolute zero), or of the reflective type, in which the radiationdetected by the video camera is derived by reflection from the lightemitted by an external source that illuminates the observed objects. Inthe case of low brightness, the detected radiation is amplified with animage intensifier (designated hereinafter with the symbol I²).

Since image intensifiers can also detect radiation in the near infrared,a preferred embodiment of the invention comprises not only an infraredvideo camera (designated hereinafter also with the expression “IR videocamera”) and a video camera that operates in the visible-light range(designated hereinafter also as “VIS video camera”), but also an imageintensifier that operates as an alternative to the VIS video camera,depending on the conditions of the degree of brightness of theenvironment to be monitored. In particular, the generic stationactivates for daytime vision a thermographic video camera in combinationwith a visible-light video camera, while for night vision it activatesthe thermographic video camera in combination with an image intensifier.

This use of vision in different spectral domains is an example and isnot exclusive to the generic station.

In each station that comprises multiple video cameras that operate indifferent spectral regimes, the video cameras are mutually coupled, havea single viewpoint and are connected to a single electronic circuit forprocessing the acquired signals, which collects the images taken in thevarious spectral domains, processes and sends them to the display or, byway of the communication means, sends them to other stations, forexample to a station that is mounted on a vehicle or helmet of a rescueror on a portable system.

With reference to FIG. 2 a, the means for communicating the acquiredimages of a mobile station comprise a transmitter 21 a in order totransmit by radio at least one video signal of a respective video cameraof the mobile station over a respective communication channel, areceiver 22 a for receiving by radio at least one video signal thatarrives from another station, and at least one aerial 23 a forbi-directional communication with the mobile stations.

In greater detail, the transmitter 21 a transmits at a certain carrierfrequency (f_(P)) a first video signal (that originates from a videocamera of the station) on a first channel Φ_(1,1) and optionallytransmits another additional video signal that originates from anothervideo camera of the station on a second channel Φ_(1,2).

Hereinafter, the reference sign Φ_(i,j) designates the generic channelon which the stations transmit and receive video information, where i=1,2, . . . , N designates the identification number of the transmittingstation, N indicates the number of total stations (fixed plus mobilestations) and j=1,2 depending on whether the video signal originatesfrom a video camera of the thermographic type (j=1) or from avisible-light video camera or from a video camera with image intensifier(j=2).

In order to reduce the number of channels used, the IR and VIS videosignals can be multiplexed before being transmitted by radio.

The circuit shown in FIG. 2 a furthermore comprises a multiplexer (MUX),by means of which the two video signals (for example the infrared andvisible-light signals) of the individual station can be multiplexed on asingle channel by using known methods. In this case, only one of the twosignals, typically the video signal that originates from the infraredthermal camera installed on the mobile station, can be sent in input tothe PIP circuit, chosen at will by the operator.

Moreover, the circuit can comprise a demultiplexer (not shown in thefigure) for receiving two video signals (IR and VIS) on a singlereception channel.

An alternative embodiment comprises two circuits of the type shown inFIG. 2 a, which do not have a multiplexer; a first circuit receives ininput the video signal that originates from a video camera of the VIStype, while the second circuit receives in input the video signal thatoriginates from a video camera of the IR type.

In the more general case in which the individual station includes morethan two video cameras that are active simultaneously, the controlcircuit can be controlled by the operator in order to choose which videosignal in reception, among all the available signals, is to besuperimposed by using the PIP module described hereinafter, by means ofa circuit that is similar to the one described in FIG. 2 a.

The receiver 22 a operates on a channel that is different from thetransmission channel of the mobile station and is preferably of thetunable type, i.e., it comprises a filter for selecting the channel 29in order to operate at different receiving frequencies (for example twofrequencies f₁ and f₂).

Optionally, the receiver comprises a notch filter 24 a that is centeredon the transmission frequencies of the transmitter 21 a in order toattenuate the signal received by the transmitter 21 a of the samestation; the signal received from the transmitter 21 a, in view of itshigher power, would in fact tend to hide the signals that originate fromother stations.

The wireless communication frequencies are centered around differentcarriers, that can be arranged in a certain area (for example, centeredaround 390 MHz, 1100 MHz, 2000 MHz, 2400 MHz, 5 GHz, 10 GHz); it isoptionally possible to use simultaneously two or more carrierfrequencies with multiple transmission frequencies centered around them,since the signal transmissions can be subject to different localstandards.

The communication means further comprise means 25 a for encoding thevideo signals to be transmitted and means 26 a for decoding the receivedvideo signals, so that different stations use a same communicationchannel.

For example, encoding and decoding can be obtained by means of knownsignal quadrature and orthogonalization methods, with “Spread Spectrum”methods of the DSSS, FHSS or OFDM type, or access methods of the TDMA orFDMA or CDMA or IEEE802.11 type.

In the case of CDMA-type access, the various users are distinguished onthe same channel by assigning a different code to each user; amultiplication operation associates a numeric sequence (code) with eachsignal to be transmitted over the communication channel, with atransmission rate that is much faster than the speed of information tobe transmitted. In this manner, the code sequences of users who sharethe same channel are mutually different and scarcely correlated.

In ideal conditions, the CDMA technique allows the information retrievaloperation to cancel the effect of mutual interference and allows toextract the intended signal.

If spread-spectrum methods of the OFDM type are used, the data aredistributed over a large number of carriers spaced apart at specificfrequencies. The benefits of this method are high spectrum efficiency,recovery from RF interference, and lower signal distortion due to thefact that the transmitted signals reach the receiver by using differentpaths of different lengths. This characteristic is extremely useful inthe case of moving mobile stations, which receive signals from fixedpoints arranged at different distances that vary as the position of themobile station varies.

As a complement, or as an alternative, to the means 25 a for encodingthe video signals to be transmitted and to the means 26 a for decodingthe received video signals, in order to allow use of a samecommunication channel by different stations, mechanisms are used toencrypt the signal that is transmitted wirelessly, in order to preventits interception by unauthorized users. This encryption process isparticularly useful in the case of transmission of signals in analogform and if each video channel coincides with a distinct and definitecarrier frequency, while for digital signals the video signal cipheringand encryption process can be performed during image digitizing.

Again with reference to FIG. 2 a, the electronic processing circuit ofeach mobile station comprises an electronic circuit 27 for superimposingon the same display images that originate from different stations; thiscircuit is preferably of the PIP type.

The PIP circuit, which is preferably present only on mobile stations,allows to arrange side by side and/or display by superimposing on thesame display images that arrive from different viewpoints, in which themain image is preferably generated by the video camera of the mobilestation of the user A while the superimposed image can originate fromthe same monitored environment by means of a wireless communication thatoriginates directly from a fixed station arranged in the vicinity of theuser A, or originates from another user B who is also in the vicinity ofA and also has a similar mobile station, or finally from a remotelylocated video camera, i.e., a video camera that sends its signal overfiber optics and makes it available at another terminal of thesurveillance system where there is A, who would otherwise not haveaccess to these video images. The PIP circuit superimposes the imagethat arrives from the thermographic video camera of the user (oralternatively that arrives from the visible-light video camera of theuser) with the image that arrives from another station on the samedisplay. In the other cases it allows to superimpose perfectly imagesthat arrive from a same optical axis or optionally to arrange them sideby side.

The electronic processing circuit further comprises means for recordingvideo information, particularly a digital recorder 28 a with hard diskrecording means 28 b.

Optionally, the electronic processing circuit comprises a microphone anda loudspeaker (not shown in the figures) that are connected thereto inorder to acquire and play back audio signals. In this case, the audiosignals also can be shared among the various stations of the system.

The electronic processing circuit is completed by a controller formodifying the controls according to the requirements of the user and bya battery.

With reference to FIG. 2 b, the means for communicating the acquiredimages comprise a transmitter 21 b, a receiver 22 b, an antenna 23 b forcommunicating with the mobile stations, and a unit 201 forelectrical/optical-optical/electrical (E/O-O/E) conversion forconverting the electrical signal processed by the circuit into anoptical signal to be sent over fiber optics and for converting theoptical signal that arrives from the fiber optics into an electricalsignal to be processed electronically.

The E/O-O/E conversion unit 201 is connected to an ADD/DROP unit 200,for adding the video image converted into an optical signal to thechannels that are present on the fiber optics (ADD function) and viceversa for selecting from the fiber optics the intended channel (DROPfunction) in order to extract video information. The ADD/DROP unit 200comprises at least one ADD module and at least one DROP module, asdescribed in greater detail with reference to FIG. 3 b.

The channels are preferably input to the fiber optics with an accessprotocol of the ATM type.

Furthermore, the fixed station comprises multiple receiving stations 22b for receiving by radio the video channels transmitted by mobilestations. In particular, if M is the number of mobile stations of thesystem and since each mobile station transmits preferably two videosignals, the multiple receiving means comprise 2M separate videoreceivers if each channel coincides with a separate transmissionfrequency or a number that is smaller than 2M if distinct transmissionprotocols are used.

Furthermore, the fixed station comprises means for selecting videosignals from the fixed network and therefore for selecting video signalsthat originate from any station of the modular surveillance system.

The means for selecting video signals from the fixed network comprise asecond receiver 22 c for receiving, by means of a control signal that istransmitted by radio, the selection of the chosen video camera of thesurveillance network on the part of the mobile station. Said controlsignal is generally at a frequency that is different from the frequencyon which the video signals are broadcast, and once it is received by thesecond receiver 22 c it activates the selection function that controlsthe routing of the video signal, as described in detail hereinafter.

The signal of the channel λ_(SEL) is then converted into an electricalsignal (designated by V_(SEL)) in the electrical/optical conversionmodule 201, is encoded by the encoder 25 b, and is transmitted by radioover a channel (designated by Φ_(SEL)), by means of the transmitter 21 bof the fixed station.

An alarm generator system (typically an external additional componentnot shown in the figure) is optionally provided on each fixed station,and in case of an alarm detected proximate to the station said systemactivates the operation of the system by means of wireless transmissionfrom the fixed stations.

Said alarm signal can be generated by an appropriate sensor or simply bythe reception of a signal of a mobile frequency received by radio. Thealarm sensor is for example a sensor of the pyroelectric type that canbe activated by abnormal heat generation; the sensor generates an alarmsignal that activates the fixed station and accordingly causes thesurveillance system to pass from a surveillance status for normalcontrol to an alert status in which all the functions of the station areactive. The alarm signal can also be generated by analyzing the videoimage of the video camera on the fixed station by means of software fordetecting the motion of people or objects in restricted areas (forexample in intrusion prevention or perimeter control systems).

In order to add flexibility to the system, the fixed station preferablytransmits by radio on at least two channels Φ_(SEL,0) and Φ_(SEL,1); onthe channel Φ_(SEL,0), all fixed stations transmit the same video signalthat originates from a video camera of the surveillance system(typically the one that is taking the most significant image and istherefore better positioned with respect to the critical area to beobserved), while on the second channel Φ_(SEL,1) the operator, from hismobile station, can select a video signal that is transmitted only bythe fixed station that is closest to him.

Since there can be multiple operators provided with a mobile station,the channel Φ_(SEL,1) is preferably selected by the rescue operator, whohas priority privileges for actuating the channel change by remotecontrol.

It is possible to further increase the flexibility of the surveillancesystem by means of a transmission from the fixed station on L channelsΦ_(SEL,1), . . . , Φ_(SEL,h), . . . , Φ_(SEL,L)), one for each mobilestation, which correspond to the total of the L mobile stations that arepresent and are able to select the video channel that they wish toreceive, by virtue of a control signal sent by radio. In this case, thecontrol signal is sent by the generic mobile station h on the channelΦ_(CTRL,h), which identifies the operator h by means of a code; everytime an image change command is sent from the mobile station h, thefixed station on the transmission channel Φ_(SEL,h) changes the videocamera that originates the video signal.

By means of access methods (for example the CDMA or OFDM methods), it ispossible to further increase the number of distinct channels that can betransmitted simultaneously from a fixed station and correspond todistinct video cameras of the surveillance system, accordingly reducingthe frequency band required for radio communications.

For fiber-optic communications, ATM-type access techniques are usedpreferably, or it is possible to use other access protocols or aplatform of the IP type, in which each mobile and fixed unit isidentified by a specific IP code.

In order to complete the flexibility of the fixed station, there is acontrol signal for traversing the video camera system related to thefixed station.

FIG. 3 a illustrates the electrical connections of the variouscomponents of the electronic processing circuit in the case in which themobile station is a helmet; the same figure also illustrates an optionalPC block 36, for processing performed directly at the station.

A supporting unit 31 is mounted on the rear part of the helmet and hasin input a plurality of signals that arrive from the front part of thehelmet; video cameras, displays, and a control box are in fact mountedon the front part of the helmet in order to select the channels; thesesignals include the control signals 32 that arrive from the control boxin order to select channels and the signals 33 for controlling the PIPcircuit, the video signals that arrive from a first video camera 34 andfrom a second video camera 35, and the power supply signal, whicharrives for example from a battery or system of batteries 37.

The system of batteries 37 is of the high-capacity type and ispreferably composed of mutually equivalent batteries (in terms of shape,type and voltage), of the commercial type. Furthermore, the power supplysystem is capable of accepting also an additional external power supply,which if present disconnects the power supply provided by the powersupply block 37 mounted on the portable system.

The input signals of the unit 31 are routed toward the variouscomponents of the electronic circuit. In the embodiment of FIG. 3 a, thefirst video signal 34 is routed toward an amplifier block 38, which isconnected to the PIP circuit 27, to the computer 36 and to the encoder25 a.

The unit 31 is further connected to the computer 36 in order to send thesecond video signal 35 directly to the computer 36 and to send theprocessed signal back to the unit 31 for local use.

The channel selection signal 32 is instead sent to the tunable filter29, which is connected to the receiver 22 a in input and to the decoder26 a and the encoder 25 a in output.

Finally, the decoder 26 a is connected both to the PIP circuit (in orderto superimpose the received image and the image encoded in the firstvideo signal 34) and to the computer 36 (in order to perform furtherprocessing).

The PIP circuit 27 receives in input the PIP control signal 33 from theunit 31 and an additional control signal from the computer 36.

Finally, the computer 36, or as an alternative the PIP circuit, isconnected to the image recording means 28 a and 28 b in order to storethe first video signal 34 after the processing of the computer 36 or thevideo signal 27 a that is output by the PIP circuit 27; the video signalpasses through the digital recorder and is resent to the display locatedin the front part of the helmet.

Optionally, there are additional connections for including a GPS signalor the measurement of sensors on the mobile station in order to detectenvironmental characteristics such as temperature, humidity, pressure,radioactivity, which can also be transmitted by means of the transmitterprovided on the mobile station.

Optionally, additional connections for transmission of audio signals canbe provided.

The connections shown in FIG. 3 a are merely a possible example of themutual connections among the various components of the electronicprocessing circuit of a mobile station.

FIG. 3 b is a more detailed view of the internal connections of thevarious components of the fixed station P_(K) and of the connections tothe fiber-optics network of the surveillance system.

In order to limit the band occupied on the fiber-optics system andtherefore the number of wavelengths required, a selective transmissionand reception system is used in the manner described hereinafter. Thissystem can operate either without the ADD/DROP module, therefore using asingle wavelength with which it is possible to transmit up to jaudio/video signals and j control signals, or in combination with theADD/DROP module, which allows to increase the number of wavelengths thatare present on the network in the manners described hereinafter.

In the case of a selective fiber-optics transmission/reception system,instead of having one wavelength for each video camera connected to thesystem (therefore a considerable number of wavelengths in the case of avery large and complex network), preferably only the audio/video signalchosen by the operator is placed on the fiber-optics system. In thismanner, the number of video signals present in the fiber-optics systemdecreases from N (equal to the number of fixed stations plus the numberof mobile stations) to L (equal to the number of mobile stations withprivilege to select the video channel among all the channels that arepresent on the network).

This arrangement allows to have a virtually infinite number of fixed andmobile stations (without the option to choose the intended videochannel), while the system is limited only by the number L of operators(who can be mobile or located at the control center) who have theprivilege to select the channels to be received and act simultaneouslyon the system by virtue of the corresponding L control signals, whichare designated here by CT_(l) (l=0, 1, . . . L).

To facilitate the selection of the intended audio/video signal by theoperator, it is convenient to group appropriately, according to a treestructure, the audio/video signals that are present on the network. Thisstructure is convenient for using the system in critical environments,such as the subway system of a city, or other critical environments inwhich it is possible to group the surveillance stations into cells andmacrocells with a tree-type structure as shown in FIG. 3 b.

Each traffic station is identified by a value S_(i) and comprises acertain number K of fixed surveillance stations, designated by P_(k),where k=1, 2, . . . K. Each station P_(k) comprises L+1 audio/videosignals T_(l) (where l=0, 1, . . . ,L).

The various traffic stations can be grouped into areas A_(h) (forexample one area for each subway line), which in turn can be groupedinto macroareas, and so forth depending on the different surveillancesystems that are to interact with each other.

Such a tree-like structure allows to identify rapidly the video camerafrom which one wishes to receive pictures according to the region whereit is located, instead of forcing the operator to scan sequentially allthe video signals available on the network until he finds the one he isseeking.

An exemplifying case of the operation of the system with K surveillancestations P_(k) with a video signal (for example IR) that originates froma video camera of the fixed station P_(k) and optionally the audiosignal that originates from a microphone installed on said station isanalyzed hereafter. In general, it is possible to add another videosignal that originates from a second video camera of the fixed stationP_(k), which operates in another spectral domain (for example in thevisible-light domain) and is associated with the first video camera inthe manner described in detail hereinafter. For the sake of simplicity,the case of a single video camera for each station, operating in asingle spectral range, is considered now.

Another L audio/video signals T₁ for each operator who has the privilegeto choose the video to be received from the fixed station P_(k) arepresent at the individual station P_(k) in addition to the video signalof the fixed video camera T₀.

Each one of the audio/video signals T₀, . . . , T_(L) of the firststation P₁ is sent to L+1 switches (designated here by P_(l,l)), whichhave L+1 inputs (T₀, . . . ,T_(L)) and 1 output.

Likewise, the signals T₀, . . . , T_(L) that originate from the stationP_(k) are sent to L+1 switches (generally designated here by P_(k,l),where k=1, . . . ,K indicates the station and l=0, 1, . . . ,L)indicates the operator provided with L+1 inputs (T₀, . . . , T_(L)) and1 output. In total, there are Kx(L+1) switches, each with L+1 inputs and1 output.

For each traffic station S_(i) and for each operator l, the structurecomprises appropriately provided control switches C_(i,l), which have ininput the control signal CT_(l) of the local operator l and the controlsignal CT_(l-RETE) generated by an operator who interacts with aremotely located traffic station that is connected to the opticalnetwork. Each switch C_(i,l) is connected in output to the opticalnetwork by means of an electrical/optical converter 301 and an ADDfilter 305 and to a decoder 303, which generates in output respectivecontrol signals CT_(l)(T), CT_(l)(P), CT_(l)(S), CT_(l)(X) for thevarious switches of the traffic station S_(l).

Considering for example the operator 0, said operator acts by means ofthe control signal CT₀(T) on the switches P_(1,0), . . . , P_(K,0). Theswitch P_(1,0) has in input the audio/video signals (T₀, . . . , T_(L))of the station 1, which are managed by the operator 0 by virtue of thecontrol signal CT₀(T).

In output, the switch P_(1,0) of the station 1 has the signal T_(l)chosen by the operator 0.

The signals that arrive from the switches P_(1,0), . . . , P_(K,0) mergein a switch of the traffic station i, designated by S_(i,0), which hasin input K audio/video signals (one for each station), the controlsignal of the operator 0 CT₀(P) and comprises, in output, the audiosignal A^(P) ₀ and/or the video signal V^(P) ₀ of the chosen station. Inthis manner, the operator 0 has chosen the station from which theaudio/video signal is to be received and the video camera or radioreceiver from which the audio/video of interest originates. The samepattern applies also to all the other L operators who have the privilegeof setting the audio/video that they wish to see.

The video signal V^(P) ₀ chosen by the operator 0 and present in outputfrom the switch S_(i,0) is input to a switch F_(i,0), which is connectedin input to an optical/electric (O/E) converter 302, which in turn isconnected to the optical network by means of a DROP filter in order toreceive the audio/video signals from remotely located traffic stations,and to the switch S_(i,0). The switch F_(i,0), moreover, is connected inoutput to the electrical/optical converter 301 and to the radiotransmitters TX₀ of the K surveillance stations of the traffic stationS_(i).

In terms of signal, the switch F_(i,0) comprises in input theaudio/video signal V^(F) ₀ that originates from the optical network, inparticular from another traffic station S_(j) (with j≠i), the signalV^(P) ₀ in output from S_(i,0), and the control signal CT₀(S), andcomprises in output a video signal V^(S) ₀ that is equal to the signalV^(P) ₀, if the control signal CT₀(S) has selected the traffic stationS_(i), or to the signal V^(F) ₀, if the control signal CT₀(S) hasselected another traffic station S_(i).

The chosen video signal V^(S) ₀ is then sent to the electric/optical(E/O) converter 301 for transmission over the network, and to thetransmitters TX₀ of each one of the K surveillance stations of thetraffic station S_(i), which in turn transmit the chosen video signalover the channel received by the operator 0.

As mentioned earlier, the control signal CT₀ can originate from one ofthe K surveillance stations of the traffic station S_(i) or canoriginate from the network (CT_(0-RETE)) if the control signal isreceived from another traffic station S_(j), i.e., if the operator 0 istransmitting from another traffic station different from S_(i).

The electric/optical converter 301 that receives the video channelassociated with the operator 0 can therefore receive also the controlsignal CT_(0-RETE) associated with said operator.

The control signal CT_(0-RETE) and the signal CT0 are provided at theinput of a switch C_(i,0). If the signal CT₀ is zero (i.e., if operator0 is not in the traffic station S_(i)), the switch C_(i,0) selects thecontrol signal CT_(0-RETE) as the control signal to be sent to all theswitches of the traffic station S_(i) by means of the decoder 303. Ifthe signal CT₀ is different from zero and therefore contains informationregarding the address of the video camera of interest (i.e., theoperator 0 is in the traffic station S_(i)), the switch C_(i,0) selectsthe control signal CT₀ as the control signal to be sent to all theswitches of the traffic station S_(i).

The signal in output from the switch C_(i,0) is sent to theelectric/optical converter 301 together with the selected audio/videosignal (A^(S) ₀, V^(S) ₀) and introduced in the network by means of theADD filter 305.

The result is that on the network there is always the control signalCT_(0-RETE) of the operator 0, which acts on all the switches of thenetwork, selecting the intended traffic station, station and videocamera, and the audio/video signal that originates from the chosen videocamera. Said signal, present on the entire network, is available and istransmitted by all the transmitters TX₀.

The same structure described above is repeated for the remaining Loperators who have the privilege to interact with the surveillancesystem. Therefore, on the network there are, in the fiber-optics system,L+1 audio/video signals and L+1 control signals, introduced with thesame methods described above.

In order to reduce the interference of the transmitted signal due toelectromagnetic overlaps from adjacent surveillance stations, it ispossible to integrate the decoder 303 with a comparator of the levels ofthe control signals CT₀ that arrive from the various surveillancestations K and are received by the decoder 303 and with a switch T_(i,0)of the traffic station S_(i). The switch T_(i,0) is connected in inputto the output V^(S) ₀ of the switch F_(i,0) and is connected in outputto the radio transmitters of the K surveillance stations of the trafficstation S_(i).

Decoder 303 generates a signal CT₀(X) that indicates the station thatreceives the strongest signal CT₀, which is sent to the switches T_(i,0)in order to select the individual transmitter TX₀ of the station P_(x)that receives the strongest signal CT₀, and therefore the station thatlies closest to the operator 0.

With commercially available fiber-optic transmission systems it ispossible to obtain easily eight channels for audio/video and forassociated controls multiplexed on a single wavelength. The possibilityto add multiple wavelengths transmitted in the same fiber by virtue ofCWDM or DWDM methods allows to create networks with a large number ofoperators, who can interact simultaneously and use the chosen videosignal picked up from the network or from any other operator, thusmaking available a virtually infinite number of separate video signalswith a low system cost.

Each station, in addition to sending an audio and video signal, canoptionally send data related to the station to which the selected videosignal belongs; these data can be superimposed on the video image byvirtue of the PIP system; the signal in output from the PIP componentcan then be encoded by means of the encoder 25 a or 25 b and thentransmitted over a channel in the manners described earlier. The datasignal management methods would be, in this case, the same as those ofthe audio signals associated with the video signal of a video camera ofa station.

Optionally, it is possible to send over the transmission channel of thefixed video camera, instead of an audio signal, data that originate fromoptional sensors of the fixed station, with environmental information(temperature, humidity, radioactivity, presence of toxic or noxiouspollutants, and others) and processing performed by virtue of additionalelements not shown in the figure, such as for example a rangefinder fordetecting the distance of the station from the site of the accident,optionally in combination with an angle measurement system (for exampleof the gyroscopic type) that can accordingly provide a more accuratelocation of the site of the accident.

These signals are also added to the fiber in the manner describedpreviously.

The system of switches described for the operator 0 is repeated for allthe other L operators. For example, for the operator 1, the station P₁sends the audio/video signals (T₀, . . . ,T_(L)) to the switch P_(1,1),on which the control signal CT₁(T) acts. According to the controlsignal, one of the audio/video signals is sent to the traffic stationswitch S_(i,1), which in turn is connected to a switch F_(i,1), and soforth, as for the operator 0.

If in the station P_(k) there are j video cameras, fixed or mounted onmobile surveillance stations that operate in different spectral domains,the total number of signals in input to a switch P_(k,l) is equal toj•L. The process for selecting the signal to be received remains thesame as the one described earlier.

Each receiver module of a fixed station P_(k), shown schematically inFIG. 3 b as the module l that has in output the signals T_(l) andCT_(l), is composed of a system for receiving the video signal and theaudio signal from the mobile station M_(h,j) on the channel Φ_(h,j),which has in input a notch filter meant to eliminate or mitigate theexcessive intensity of the carriers of the frequencies emitted intransmission by the station P_(k), received due to the mutual proximityof the receiver and the transmitter. The same module l includes a secondreceiver for receiving on another service channel the image changecontrol signal related to a separate video camera, whose signal ispresent in the surveillance network. On the channel on which the controlsignal is present there may be other complementary information relatedto the mobile station, such as for example the location of the mobilestation, detected by means of the GPS system provided on the mobilestation, or environmental information again related to the mobilestation (temperature, humidity, radioactivity, presence of toxic ornoxious pollutants, and others) or control of traversal by the mobilestation or of the focus of the video cameras of the fixed station P_(K)from which the mobile station receives the picture, in order to improvethe visibility of the area of interest.

The channels used by radio are two for each operator equipped with asingle video camera (one channel in transmission and one channel inreception for each video signal). If the individual mobile stationgenerates more than one video signal (for example if it comprises videocameras that operate in different spectral conditions), said signals aremultiplexed, as shown, through a multiplexer and are transmitted on asingle channel or on two separate channels.

The number of radio channels required for L operators, each providedwith j separate video cameras, is q_(max)=2j×(L+1), considering anadditional channel Φ_(SEL,1) on which the signal of the most significantvideo camera is transmitted, optionally with the addition of informationon the part of a control center that is available to all stations thatare enabled to receive the video signal.

As it will be explained with reference to FIG. 8, in the preferredembodiment the various traffic stations (either of the same or differentareas) are connected to the fiber network so as to form a ring.

Using suitable access and multiplexing techniques, the channels can bereduced in number.

The fixed station P_(K) is completed by an alarm sensor (for example ofthe pyroelectric type that can be activated by abnormal heatgeneration), which generates an alarm signal that activates the stationP_(K) and accordingly makes the surveillance system shift from asurveillance status for normal control to an alert status in which allthe described functions are active. As an alternative, it is possible togenerate the alarm by using software that detects the abnormal motion ofobjects or people and accordingly generates an alert signal.

In the mobile stations, the means for transmitting and encoding theirown signal, the means for receiving and decoding the signals of otherstations and the PIP circuit constitute a self-sufficient module that isremovable and can be interchanged among different users.

As mentioned several times above, the information available to a usercan be increased by combining a plurality of video cameras that operatein different spectral ranges.

For example, one particular embodiment comprises a video camera 41 thatoperates in the visible-light range (VIS), a video camera 42 thatoperates in the infrared range (IR), and a video camera with imageintensifier 43 that operates in the near infrared (I²), all arranged soas to acquire the environmental image on a same optical input axis 44.

The IR video camera preferably comprises a sensor of the FPA (FocalPlane Array) microbolometric type, with resolutions that can vary from160×120 to 320×240 to 640×480 depending on the manufacturer of the IRvideo camera. As an alternative, it is possible to use IR video cameraswith InSb or quantum well sensors, the latter being optionally sensitiveto two different spectral intervals simultaneously on the same focalplane.

In order to separate the spectral components of the environmental imageand project the image onto the video cameras from a same viewpoint, thevideo cameras are arranged as in FIG. 4 a and splitter laminas are used.

According to what is shown in FIG. 4 a, the video cameras 42 (IR) and 41(VIS) are mounted on the station in perpendicular acquisitiondirections, while the video camera 43 (I²) is mounted in an acquisitiondirection that lies at right angles to the plane on which the other twovideo cameras are arranged.

An input eyepiece 45 is mounted in axial alignment with the acquisitiondirection of the IR video camera; a first splitter lamina 46 fortransmitting infrared frequencies and reflecting the other frequenciesis mounted in axial alignment between said input eyepiece and the lensof the IR video camera, with an inclination of 45° with respect to thedirection of acquisition of the IR video camera.

A second splitter lamina 47 for transmitting near-infrared frequenciesand reflecting the other frequencies, is fitted at the intersectionbetween the direction of acquisition of the VIS video camera and thedirection of acquisition of the I² video camera, with a 45° inclination.

Optionally, there are additional filters of the interference oracoustooptical type for reducing selectively the spectral band in inputto the video camera; said filters are not shown in the figure.

The optical path between the input eyepiece 45 and the lens of eachvideo camera must be the same for all the video cameras, and so musttheir viewing field, so as to have a correct overlap of the images inthe various spectral domains; it is possible to insert suitable opticalsystems before the lens of each video camera in order to compensate forvariations caused by the different dimensions of the FPA sensors of eachvideo camera and by the different behavior of the lenses in distinctspectral domains.

On the basis of the arrangement described above, it is possible to sendthe spectral components of an environmental image to the respectiverelevant video camera.

A lens with an optical zoom and adjustable focus (48 a, 48 b, 48 c),both preferably motorized, is mounted in front of each video camera soas to be able to scale appropriately the size of the picture and allowthe perfect overlap of images of different spectral domains. For thispurpose it is possible to take a common reference (FIG. 4 b) that allowsto calibrate appropriately the size of the images and accordingly theappropriate magnification ratios in the various spectral domains inorder to achieve the intended overlap. The filament with four disksshown in the figure is made of a material that is opaque to radiation ofthe spectral domains into which the radiation is split (for exampleopaque to heat radiation and to visible radiation) and is arranged onthe eyepiece 45, which is transparent to the spectral domains beingconsidered, and is removable. This allows to correlate the focus of thevarious video cameras and to set a proportionality coefficient thatallows the perfect overlap of the images of different spectral domains.

As an alternative, other forms of calibration with removable targetsarranged at a certain distance (for example 7-10 meters) are considered;these calibrations are performed during production instead of directlyin the field.

The particular arrangement of video cameras and splitter laminasdescribed above is merely an example, and many other arrangements can beproposed in the light of this particular arrangement according to theknowledge of a person skilled in the art.

By means of the PIP circuit included in the station, the picturesacquired by the three IR, VIS and I² video cameras can be arranged sideby side or perfectly superimposed on a single display, wherein, asexplained earlier, the VIS video signal is an alternative to the I²signal in the case of daytime and nighttime vision respectively. Othertypes of video camera combinations that operate in different spectraldomains and other methods for displaying a picture on a display are inany case possible without losing the possibility to superimpose thanksto the fact that all the video cameras have the same optical axis.

In the case of single-display viewing, said display can be a commercialbacklit one, for example of the TFT type, or of the self-emitting type,such as OLED (Organic Light Emitting Display), and in general saiddisplay is not transparent. If a transmissive-type display (TOLED,Transmissive Organic Light Emitting Display) is used, viewing throughthe display is possible with overlap of the picture that arrives fromthe video camera, typically the infrared thermal cameras.

As an alternative, it is possible to use two superimposed displays, ofwhich at least one is transparent and is based on organic light emissionand is of the transmissive type (TOLED, Transmissive Organic LightEmitting Display) or of the flexible type (FOLED, Flexible Organic LightEmitting Display), as shown in FIGS. 6 a-6 c.

In greater detail, a first transparent display 61 is mounted in theforeground with respect to the viewpoint of the user, and a seconddisplay 62 (for example an LCD or FOLED) is mounted in the backgroundwith respect to the user's viewpoint. By means of the control circuit,the pictures acquired by the IR video camera are displayed on the firstdisplay 61 and the pictures acquired by another video camera (VIS or I²)are displayed on the second display 62.

It is possible to superimpose IR pictures displayed on the first displayand VIS pictures displayed on the second display, and it is alsopossible to superimpose images that arrive from other stations with aPIP method.

If the mobile station receives, from a mobile or fixed station, avisible and IR video signal on a dual channel, the same type of displayof pictures on superimposed displays can be used also on the PIP imagedisplayed together with the actual image, wherein the display 61displays thermographic images and the second display 62 displays imagesin the visible domain, according to the same type of PIP (the dimensionand position of the PIP frame coincide in the two displays).

Since the display is close to the eyes, in order to limit the negativeeffect of electromagnetic emission on the eyes, a screen (not shown inthe figures) is optionally interposed which has an integrated mesh ofconducting material that allows to limit the electromagnetic stressaffecting the eyes of the user.

Moreover, in mobile and fixed stations there are advantageouslyremovable modules for expanding the viewing field of the user.

With reference to FIG. 5 a, in order to deflect the viewing field of atleast one video camera 54 or of a system of video cameras such as theone described above, there are first of all means for deflecting theenvironmental image 51 that are mounted upstream of said video camerasof the station. The deflection means 51 comprise in particular motorizedmeans and a mirror 52 that is mounted on them in order to reflect theenvironmental image onto the video camera along a plurality of anglesand consequently expand the viewing field.

The mirror 52 ideally reflects radiation at wavelengths comprisedbetween approximately 400 nm and 14 μm.

The motorized means, in the preferred embodiment, consist of agalvanometer 51 a on which the mirror 52 is mounted; the mirror ismounted so that it lies on the same axis of acquisition 53 as the videocamera 54 and can rotate, under the control of the galvanometer, betweentwo extreme angular positions 52 a and 52 b (with inclinations, withrespect to the normal to the acquisition axis 53, of α_(max) and α_(min)respectively). In this manner, the environmental images reflected by themirror 52 in the various angular positions are acquired by the videocamera 54 and are displayed on a display, increasing the viewing field.If θ is the angle of the viewing field of the video camera, the newextended viewing field is equal to N_(FOV)=(α_(max)−α_(min)+0); if forexample θ coincides with the deflection angle of the galvanometer(α_(max)−α_(min)), the viewing field is doubled.

If the oscillation frequency of the galvanometer is low (typically 0.5Hz), a rotating image is displayed on the display.

With a higher oscillation frequency it is instead possible to display asingle picture; in order to allow synchronization with the PAL and NTSCsystems, the preferred oscillation frequency of the galvanometer iscomprised between 25 and 30 Hz. Image acquisition occurs by means of ashutter 57 (FIG. 5 a) that is arranged outside the image input cone, issynchronized with the intended acquisition position and operates attwice the oscillation frequency of the galvanometer (50-60 Hz), in orderto allow two acquisitions in two points according to an angle α_(max)and α_(min) respectively.

The dimensions of the display must be such as to allow viewing of thetwo images side by side; as an alternative, the two images can bedisplayed respectively on two displays arranged side by side.

The deflection system is preferably mounted in fixed stations and isused as an alternative to traversal in the case of limited rotationangles; in particular, it becomes particularly useful if it is used as arapid aiming system for fixed stations, orientating the viewing field inthe intended direction by rotating the mirror on the galvanometer,instead of turning the traversal, with an enormously faster response andrepositioning speed.

As an alternative, the viewing field can be extended in one direction bymoving along a guide the video cameras of the station (which aremutually rigidly coupled), according to an oscillation that can be forexample sinusoidal. The video camera system does not rotate about itsown axis but traces a circular arc-like path on the guide that issimilar to the circular path traced by the eyes with respect to therotation point of the neck. The radius is determined by the distance ofthe eyes from the neck, which is typically 20 cm, and the length of thecircular arc depends on the intended viewing field. If θ is the cornerof the viewing field of the video camera, the new extended viewing fieldis equal to N_(FOV)=(2α+θ).

The oscillation frequency can vary according to the type of use of theimages acquired by the video cameras. A slow oscillation (frequencylower than 5 Hz) is used to show the field with a 4:3 display and sothat the full image fills the entire display. It is also possible to usea wider display in which the image moves according to the rotationperformed.

With reference to FIGS. 5 b and 5 c, it is possible to improve theuser's vision by adding to the deflection means 51 described above meansthat allow stereoscopic vision.

The means for stereoscopic vision comprises two eyepieces 55 a and 55 bfor acquiring environmental images from two symmetrical viewpoints thatare orientated parallel to the same optical axis of acquisition 53 asthe video camera (FIG. 5 b).

Each eyepiece is coupled to a respective reflective means 56 a and 56 b(for example another mirror), which is inclined with respect to theoptical input axis 53 by an angle γ in order to reflect theenvironmental image onto the mirror 52 that is mounted on thegalvanometer. These reflective surfaces 56 a, 56 b and 52 are notnecessarily flat, but can be curved and therefore able to better focusthe image onto the video camera, in order to reduce the dimensions ofthe reflective surfaces and of the optical systems, in order to containthe entire viewing field of the video camera.

In the embodiment shown in FIGS. 5 b-5 d, the angle γ coincides with theangle α of maximum mechanical rotation of the galvanometer (typically±20°). Other configurations are of course possible in which γ isdifferent from α; if y<α it is possible to achieve improved peripheralvision.

Optionally, due to speed and image stability requirements, the angle γcan be smaller than the angle α of maximum rotation of the galvanometer.

As shown in FIG. 5 c, the optical elements cited so far, i.e., the twoeyepieces 55 a and 55 b, the mirrors 56 a and 56 b, the deflectingmirror 52 mounted on the galvanometer and the video camera 54 are notall arranged on the same plane but are arranged spatially on twoseparate planes that can be parallel or mutually inclined. Theembodiment with two parallel planes is shown in FIG. 5 c.

The embodiment shown in FIG. 5 c illustrates an optional lens system 58a and 58 b for improving picture quality, which can be inserted easilywithout compromising the functionality of the other elements thatcompose the stereoscopic vision system; arranging additional elementswithin the optical path has the immediate consequence of extending saidoptical path and therefore forces larger dimensions for the opticalelements arranged along the path.

The arrangement of the various optical elements on two separate planesallows to reduce considerably the length of the optical path in relationto the size of the video camera lens and of its viewing field, which arefixed parameters set by the manufacturer.

FIG. 5 d in fact deals with the problem of the size of optical systemsand of their positioning depending on the deflection angle α of themirror mounted on the galvanometer, on the aperture of the lens A of thevideo camera, of the thickness h_(o) of the enclosure of the lens, andof the viewing field of the video camera θ.

To prevent the image reflected by the mirror 52 from interfering withthe lens of the video camera 54, the distance w between thecorresponding outer radius that limits the viewing field of the videocamera and the lens A of the video camera is greater than the valueh_(o) of the thickness of the container of the video camera, i.e.,w≧h_(o). To allow this condition to occur, if L is the distance betweenthe aperture of the lens A and the center of the mirror 52 (located atthe galvanometer axis), said distance must be greater than a minimumvalue that allows to have w≧h_(o). The minimum value of L obtained forw=h_(o) corresponds to L_(min) and is directly proportional to theaperture A, to the thickness of the mount h_(o), and to the width of theviewing field θ, while it is inversely proportional to the angle α ofdeflection of the first mirror upstream of the video camera, accordingto the formula

$L_{\min} = {\left\{ {{\left( {A + h_{o}} \right) \cdot \frac{1 + {\tan(\alpha){\tan\left( {\theta/2} \right)}}}{{\tan\left( {{2\alpha} - {\theta/2}} \right)} - {\tan\left( {\theta/2} \right)}}} + {\frac{A}{2} \cdot {\tan(\alpha)}}} \right\}.}$

On the other hand, one must consider that the inclination a leads, ifgreater, to a limit value that makes the mirror 52 collide against thelens 54.

It is demonstrated that an optimum inclination a in the case of athermal camera with a lens having an aperture of 25 mm and a verticalviewing field θ=12° is on the order of 40°. This allows to have L_(min)values on the order of 20 mm.

Another important parameter for the image deflection system is thedimension d of the mirror mounted on the galvanometer, which isdemonstrated to be proportional to the aperture A, to the distance L andto the angle α of maximum mechanical rotation.

The mirror 56 a is generally larger than the mirror 52 and itsdimensions, as well as its position, are both demonstrated to be afunction of the parameters cited above and of the angle γ, which canalso have values different from α.

The dimension of the input eyepiece 55 a is proportional to the totalpath comprised between the aperture A and the aperture 55 a, and to theviewing field θ.

The remarks made with reference to FIG. 5 d apply likewise to thediagrams shown in FIGS. 5 b and 5 c, where in the case of FIG. 5 b oneconsiders FIG. 5 d as a detail view of the left eyepiece of thestereoscopic system, while in the case of FIG. 5 c one considers FIG. 5d as a detail view of the lateral vision rotated through 90°.

In view of what has been described above, it is evident that since thegalvanometer in general has a maximum range of the deflection angle of±20°, it would force an excessive length of the optical path of thestereoscopic system if all the optical elements were arranged on thesame plane. The fact of having two separate planes on which the opticalelements are arranged allows to apply also laterally (FIG. 5 c) the sameremarks made with reference to FIG. 5 d and to incline the galvanometerby an optimum angle (as mentioned earlier, 40°) regardless of the rangeof the galvanometer. Furthermore, thanks to the fact that the width ofthe vertical viewing field θ is generally smaller than the horizontaldimension, there is an additional benefit in terms of compactness of thesystem and of reduction of the dimensions of the optical systems.

With a galvanometer oscillation frequency preferably comprised between25 and 30 Hz, the images are acquires alternately by one eyepiece and bythe other; the acquired images are reflected toward the video camera,superimposed and displayed on the display with a frequency of 50-60 Hz.

The mobile stations that comprise the means for stereoscopic visioncomprise a display whose dimensions are sufficient to allow viewing withboth eyes, for example 5 inches.

As an alternative, one display for each eye is used in order to obtain astereoscopic vision in which each display receives the image from therespective eyepiece due to the synchronization provided by theelectronic control system, which sends to the left display the imagesthat arrive from the left eyepiece, which are received when thedeflection angle of the galvanometer has a value −α and vice versa forthe right eyepiece. Even in the case of binocular vision, it is possibleto use for each eyepiece two superimposed micro-displays, at least oneof which is of the TOLED transmissive type, with the types describedearlier.

The PIP circuit, the video cameras operating in different spectraldomains with the same optical axis, and the removable modules forexpanding the viewing field of the user constitute the three componentsfor improving the user's vision of the monitored environment.

By combining vision from different spectral domains with the possibilityto obtain three-dimensional images (3D), it is possible to obtain, withtwo superimposed displays according to the methods already described,the following combinations:

a first display with a 2D visible-light image and a second display witha 2D black and white/color IR image;

a first display with a 2D I² image and a second display with a 2D blackand white/color IR image;

a first display with a 3D visible-light image and a second display witha 2D color or black and white IR image;

a first display with a 3D visible-light image and a second display witha 3D color or black and white IR image;

a first display with a 3D I² image and a second display with a 2D blackand white/color IR image;

a first display with a 3D I² image and a second display with a 3D blackand white/color IR image.

FIG. 6 a illustrates a mobile station on a helmet 60. As explainedpreviously, a first transparent display 61 is mounted in the foregroundwith respect to the user's viewpoint, and a second display 62 (forexample LCD or FOLED) is mounted in the background with respect to theuser's viewpoint. The first display 61 is connected to the IR videocamera and the second display 62 is connected to the VIS video camera.

The IR and VIS video cameras are mounted in the front part of the helmetand are illustrated schematically by the block 63.

The mobile station is mounted on a helmet by means of a supportingstructure or adaptor 65 that comprises a front support 65 a, a rearsupport 65 b, and a connector that is external to the helmet 65 c.

The video cameras 63, the control box and the displays 61 and 62 aremounted on the front support 65 a.

The battery 37, the audio/video transmitter/receiver, the digitalaudio/video recorder (or alternatively a microcomputer) and anybalancing weights, depending on the number of components that arepresent on the front support 65 a, are mounted on the rear support;preferably, the communication means (designated by the reference numeral66 in FIG. 6) are mounted on the rear support 65 b.

The rear support is completed by coupling elements 67 for fixing thesupporting structure 65 to the helmet.

The advantage of this system is that it can be anchored to the helmetwithout requiring modifications or holes in the helmet in order toprovide stable fixing, thus maintaining the original type approval ofthe helmet. This system of adapters therefore does not require a newtype approval for the protection provided by the helmet, since it hasthe same impact as a peak applied externally to the helmet.

A preferred embodiment of a helmet provided with an anchoring device 65is shown in greater detail in FIG. 6 d.

The front part 65 a of the anchoring device comprises a front adapter68, which substantially has the shape of a rigid peak which, when fittedon the helmet, protrudes substantially at right angles to the frontregion of the helmet. The adapter 68, also termed “peak” herein,comprises an undercut 65 d, while the rear adapter 65 b comprises anundercut 65 e.

The undercut 65 d is shaped complementarily to the edge and/or frontsurface of the helmet, while the undercut 65 e is shaped complementarilyto the edge and/or rear surface of the helmet.

Preferably, the peak 68 is connected to the rear adapter 65 b by meansof a connector 65 c, which is preferably shaped complementarily to theupper surface of the helmet, in order to prevent any movement of thecomponents of the anchoring device with respect to the helmet. Theanchoring device thus constituted can therefore bear considerable loadsand space occupations.

The peak 68 comprises means 166, mounted thereon, for connection to thebattery and a frame 163 for supporting the video camera, the display andthe control circuits.

FIG. 6 f is a front sectional view of an example of a frame 163, whichcomprises a supporting bridge 162, which comprises video camerasupporting means 167 that are arranged substantially centrally withrespect to said bridge 162, and comprises anchoring elements 163 a, 163b for the detachable fixing of the frame 163 to the peak 68.

The anchoring elements 163 a and 163 b are arranged at the opposite endsof the bridge 162 and are suitable to be inserted slidingly on the peak68 by means of hooks 164 a and 164 b. The anchoring elements furthermorecomprise respective flanges, which are directed downward orsubstantially at right angles to the peak 68 and comprise pivots 168 a,168 b, in order to support rotatably at least one display 170.

Optionally, the anchoring elements 163 a and 163 b comprise grub screws(screws which have a retractable ball on one end) 165, which can engagethe display or the supporting structure of the display 170 in order tolock its position.

As an alternative to the grub screws, in order to lock the rotation ofthe display about the pivots 168 a and 168 b it is possible to use handscrews 177 or other locking means that are clearly within the grasp ofthe person skilled in the art.

The means for supporting the video camera 167 are fixed to the bridge162 and preferably comprise at least one hermetic front connector 167 afor electronic connection to a video camera, at least one hermetic rearconnector 167 b for the wired electronic connection of the video camera,of the display and of the control circuit to the battery (which ismounted on the rear part 65 b of the anchoring device), and finally adovetail joint 167 c for mechanical fixing of the video camera 169 tothe support 167.

The display 170 can be connected directly to the video camera or, as analternative, to an additional connector provided on the video camerasupporting means 167.

In an alternative embodiment, not shown, if the helmet already has arigid peak, the front part 65 a of the anchoring device does notcomprise a peak but comprises only a frame that is similar to the frame163 that can be fastened to the peak of the helmet.

The fact that mounting on the helmet is not direct but occurs preferablyby means of an adaptor is due to the convenience of being able to betteradapt the vision system (video cameras, display, transceiver device andbattery) to any type of helmet without the need to provide a completehelmet unit. Rescuers and law enforcement agents in fact already haveprotective helmets that are specifically studied and certified for theircorresponding use. The advantage of not having to redesign the helmetlies in the manufacturing cost saving (each mold of an entire helmetentails high development and certification costs). In order to be ableto adapt the vision system to any kind of helmet and to further limitthe costs of this adaptation, the vision system is not mounted directlyon a helmet but is indeed mounted on an adaptor or auxiliary support 68.

The function of this auxiliary support is to always have the sameinterface for mutually connecting (mechanically and electrically) thevarious modules of the vision system, while the part for fixing to thehelmet changes according to the kind of helmet.

This allows economy in manufacturing on the part of the manufacturer,since instead of having to manufacture countless different containersfor the vision system, it is possible to produce a single container thathas the same mechanical shape, with the electrical connections arrangedaccording to a standard layout. This also allows economy on the part ofthe user organization, since operators of a same organization or even ofdifferent organizations, be they police corps, firefighters or militarypersonnel, who use helmets of different shapes, can use the same visionsystem, with the only expense of the adaptor for their type of helmet,adding flexibility without affecting costs.

In the embodiment shown in FIG. 6 a, the two displays are mounted sothat they can rotate on the front support 65 a, so that they can belowered or raised by the user in order to allow direct vision.

FIG. 6 e schematically illustrates an assembly for mechanical rotationof the display according to a preferred embodiment of the invention, inwhich the coupling between the display and the peak is of thepin-and-guide type.

In particular, the display is integrated with a support 170 andcomprises, on two opposite side walls 172, respective guides 171. Theguides 171 consist of linear slots, but it is equally possible toprovide grooves or other guiding means capable of allowing a combinedrotary and translational motion of the display 170 with respect to thepeak 68 and the frame 163.

The pin-and-guide coupling allows the display 170 to assume two extremepositions, particularly a horizontal position that is close to thehelmet, in which the display lies substantially parallel to the peak,and a vertical position that is spaced from the helmet, in which thedisplay lies on a plane that is substantially perpendicular to the peak,so as to allow the operator who wears the helmet to view the images onthe display.

The side walls 172 of the display 170 optionally comprise recesses 174(or, as an alternative, protrusions) for interacting with the grubscrews 168 a and/or 168 b, so as to adjust the position of the displayat various inclinations with respect to the vertical position.

In the embodiment shown in FIG. 6 d, the walls 172 comprise a threadedhole that is suitable to accommodate the hand screw 177.

The horizontal position of the display is maintained by means of theretention provided by the peak 68.

The display 170 preferably has a rounded shape at the edge that slideson the frame 163 during rotation, so as to allow easy rotation.

The grub screw must be arranged inside the circle 175 that is centeredon the pin and has a radius equal to the distance between the center ofthe pin and the viewing surface of the display, when the support 170 isin the horizontal position. The distance between the stroke limitposition and the guide 171 of the support of the display is equal to thedistance of the grub screw from the guide of the display when thedisplay is in the horizontal position.

The connection between the display and the support 166 occurs by meansof a cable with IP68 hermetic terminals. The cable is sheathed withmaterials that increase its resistance to heat and to corrosive agents.

Each module is connected to the other module electrically by means ofnormal connectors or connectors that provide a hermetic seal up to IP69with n pins, through which all the control signals, video signals andthe power supply pass. The signals are routed by the control box 64,which allows, by means of buttons, to modify the controls according tothe contingent requirements of the user. From a mechanical standpoint,conventional locking means are used to fix the vision system to theadapter. For the sake of convenience, the control box 64 is comprisedwithin the display module 170, allowing to have the available buttonsand options in front of the operator in a simple and visible manner.

While the video camera and the display are again mounted on a peak bymeans of an adaptor, the main battery 37 is mounted by means of anadaptor that is located in the rear part 65 b of the helmet. The battery37 can be connected by means of an external electrical cable providedwith a fireproof and waterproof sheath to a battery carried in abackpack. The battery 37 fixed on the helmet can also be omitted, if themobile unit is connected directly to the battery that is present in thebackpack, and in the case of particularly dangerous areas, where it canbe used as the only power source so as to avoid problems related tooverheating of the helmet as a consequence of excessive heat sources.

In an embodiment that is alternative to the one shown in FIGS. 6 a-6 fand in particular in the case of helmets provided with a protectivepeak, a display of the FOLED type can be mounted directly inside thepeak (for example in a gas mask) due to its flexibility andadaptability.

The image received from the mobile station is displayed with a PIPsystem on the picture of one's own video camera, which is alwayspresent, as shown for example in FIG. 4 d. This allows to never losesight of what is in front of the user who is operating in emergencyconditions, and to have additional information available, displayed withthe picture-in-picture system and therefore superimposed on one's ownpicture.

If used on a helmet for private users, for example for motorcyclists,the system of FIG. 6 a is further simplified, since it comprises thesame elements provided in the system of FIG. 6 a but has a simplifiedimage processing system, i.e., without the image recording system andwith a transmission and reception system that allows to access only somechannels assigned to private users but does not allow access to channelsdedicated to law enforcement operators or to rescuers, as will becomebetter apparent hereinafter.

If used on a motorcycle helmet, the display is of the FOLED typeintegrated in the peak and is optionally removable and interchangeablewith a normal peak, or is of the TOLED type, in order to allow viewingof the road through the display, or is of the micro-display type, havinga diameter comprised between 1 and 2.5 inches and referred only to asingle eyepiece if the display used is not transparent and integratablewith a second eyepiece if the display is of the TOLED type.

The application of the concepts described up to now to the case of amobile station of the vehicle-mounted type is illustrated with referenceto FIG. 6 b.

The vehicle-mounted station comprises the same functional modules thatare present on the helmet (the same reference numerals are used for thesake of simplicity for components that have a function that is identicalto the components that have been already described); in particular, thevehicle-mounted station comprises at least one video camera 63 (which ismounted in a front position with respect to the vehicle), a battery 37(which is mounted within the engine compartment), a pair of displays 61,62 (which are mounted on the parasol), a control box 64, andtransmission and reception means 66 that are mounted inside the cabin.

As occurs in the case of the helmet used for private use or for lawenforcement, there is a difference between the law-enforcement vehicleand the private vehicle in terms of the number of channels to which itcan have access to receive pictures from the surveillance network and tosend control commands to said network. In the case of a rescue vehicle,the functional modules are exactly identical to those of the genericmobile station as shown in FIGS. 3 a and 4 a, with access to all thefunctionalities described so far, whereas for private use the signaltransmission and reception system is preferably simplified and reducedin its flexibility, allowing fully passive reception and transmissionthat can be activated in case of a critical event such as fog, fire,accident occurring in the area where the vehicle is passing, with theonly option for the user to be able to change channel (and thereforeviewpoint) by using the transmission of video cameras of thesurveillance system, including private vehicles themselves, which havesaid system and are passing in the area of interest. The system, whenactive, allows to use the pictures that arrive from vehicles located inthe area and to provide said pictures to said vehicles, with integrationof the images that arrive from the fixed video cameras. In this case itis possible to avoid accidents or to avoid approaching of regions wherethe accident has occurred at a speed that does not allow to avoid theimpact in the disaster area. This functionality is particularly usefulin the case of poor visibility due to fog or thick smoke. Rescuevehicles are given access to all the video cameras of the surveillancesystem, including those mounted on private vehicles, and additionalvision systems described hereinafter. This application is described ingreater detail hereinafter.

The display on the vehicle is preferably performed by means of a TOLEDdisplay (one or more according to the complexity of the system), whichis located in front of the driver at the sunshade and is integratedtherein. Said display can therefore move up and down as occurs in thecase of the helmet.

The modules can be composed so as to form a camouflaged system forinvestigation purposes; the system can in fact be concealed by insertingit in containers of a material that allows IR transmission (for examplepolycarbonate or other plastic materials) and has the same shape ascommercial containers that are commonly used (ski boxes to be installedon a vehicle, rigid bags on a moped or on the shoulder, et cetera),which are located in the same positions in which the actual items areplaced, with an untraceable investigation function.

By virtue of the possibility of plastic materials to be transparent tonear-infrared radiation (typically 700 nm) and far-infrared radiation(typically 3-5 microns or in some cases even 7-14 microns), while theyare opaque to visible-light wavelengths (typically 400-700 nm), it ispossible to provide portable vision units that are concealed insidecontainers that are adapted to avoid attracting attention, allowing forinvestigation purposes to take pictures even in much closer positionswithout raising the slightest suspicion.

The communication means 66 are preferably of the detachable type; inparticular, they consist of a transceiver unit of the UMTS type, whichcan be easily removed and used separately for multimedia and ordinarymobile telephone applications.

The use of the functional modules shown in FIGS. 3 a and 4 a and appliedto a hand-held portable system is shown with reference to FIG. 6 c.

In this case also, it is necessary to make a distinction between thecase of law enforcement agents from the case of a private user, since asmentioned above there will be differences in terms of the number ofchannels to which access is provided in order to receive pictures fromthe surveillance network and send control commands to said network, asoccurs for the other station types.

Both for law enforcement agents and for private users, it is possible,where available, to use the advantages of communications of the UMTStype.

If the surveillance system is connected to a UMTS network, it allows infact to send the images that originate from this system to users thatare equipped with a UMTS terminal, even a commercial one, and thereforeit allows to use images in critical situations that are made availableon dedicated channels, which are activated in critical situations andare read by terminals located in the area where the disaster isoccurring. The UMTS device is provided optionally with a button that hasthe specific function of calling for connection to the emergency serviceand of requesting the sending of images from the location where therequest is activated; i.e., if the two conditions of picture sendingrequest and of surveillance system alarm activation occursimultaneously, the transmitter of the surveillance system starts tosend pictures to the UMTS terminal that requested them.

With reference to FIG. 7, the fixed station is mounted on a support 75,and in addition to the elements shared by the various stations, such asthe video camera or the system of video cameras 63, the electroniccontrol circuit and the means for communication with the other stations66, it comprises said alarm means 74 for transmitting alarm signals toother stations, the means for electrical/optical and optical/electricalconversion 201, and the ADD-DROP module 200.

During the operation of the surveillance system, the fiber-optic networkcontains multiple channels M that correspond to a matching number ofmobile surveillance stations enabled to choose the channel to bereceived.

Each traffic station S_(i), constituted by multiple fixed surveillancestations P_(k), corresponds to a node of the fiber-optic network andinputs therein the signal of fixed video camera selected by the operatorthat corresponds to that node (there is more than one video camera, ofthe visible-light and infrared types, for each node) and the multipleaudio/video signals received by that node from the adjacent mobilestations.

The type of remote video camera, whose signal is transmitted at thefrequency f_(K) by the fixed system, is selected by means of a radiocontrol CT_(0-M) transmitted by the mobile station M_(h).

With reference to FIG. 8, the surveillance system according to anembodiment of the invention can be described in greater detail asfollows.

In reception, it is possible to receive video pictures that originatefrom a central computer (located in a control center) and contain muchmore information than the transmitted pictures, i.e., the picturesacquired by the operator M_(h) can be transmitted on the channel Φ_(hj)to a remote computer, processed and resent to the operator M_(h) at thereception frequency Φ_(SEL,0).

The surveillance system is provided with S_(i) fixed stations, each ofwhich is connected to a respective node F_(i) in a transmission network,for example a fiber-optics network, which has a ring structure and inwhich all the pictures of the video cameras are carried on fiber optics,as shown in FIGS. 1 and 8; these structures in turn can be connected toeach other, forming a cluster structure. It is possible to definemacrocells that correspond to a specific area to be subjected tosurveillance (for example a highway tunnel or a city tunnel or a woodedarea or an industrial site or a nuclear site or a shopping center with aconcentration of people), mutually connected by means of a fixed networktermed Core Network.

Consider a surveillance system composed of F=F_(IR)+F_(VIS) fixed videocameras (where F_(IR) is the number of fixed IR video cameras andF_(VIS) is the number of fixed VIS video cameras), and composed ofM=M_(C)+M_(V)+M_(P) mobile video cameras, whose number can varydepending on the active operators; M_(C) indicates the number ofhelmet-mounted mobile stations, M_(V) designates the number ofvehicle-mounted mobile stations, and M_(P) designates the number ofportable mobile stations.

The operation of the system is as follows. Each node introduces in thefixed network (Core Network) the signal of the fixed video cameras thatcorrespond to that node and the signals transmitted by the M mobilestations, which are transmitted by radio from the generic station M_(h)on two channels (Φ_(h,1) for IR and Φ_(h,s) for VIS). If a singlechannel is available, transmission for IR is preferred.

The IR or VIS video signal can be a signal of the stereographic type inorder to allow 3D display; in this case, unless video signal compressionis performed, this transmission occurs at the expense of a widening ofthe band of the corresponding channel.

In this manner, a node located in another point of the surveillancesystem can transmit by radio an image received from a fixed video cameraF_(k) or from a mobile video camera M_(h) received in any other point ofthe system. Each station is in fact simultaneously a transmitting andreceiving point.

Transmission from the node K occurs on the channel Φ_(SEL,0) and on 2Mchannels Φ_(SEL,M). Therefore, the mobile station M_(h) can receive thesignals that arrive from the other adjacent mobile stations M_(j) (j≠h),for example by means of direct transmission between for example M_(h),and M_(j) by means of the channel Φ_(j,1) and Φ_(j,2) and from the fixedstation F_(K) on the channel Φ_(SEL,h).

In the simplest case, all the nodes of the system transmit at the samefrequency Φ_(SEL,0). In general, the mobile station M_(h) receives thesignal from the most “convenient” node that allows it to have thehighest signal level. The type of video camera of a remote mobile orfixed station whose signal is transmitted is transmitted on the channelΦ_(SEL,J) by the fixed system and is selected by means of a radiocontrol transmitted by the station M_(j) on the channel Φ_(CTRL,j). Thefixed station that generates an alarm on the basis of the sensing of anexternal sensor or of a software for processing the acquired imagesintroduces the video signal in the network and transmits it to all theother nodes on the wavelength λ₀ and wirelessly to all the mobilestations on the channel Φ_(SEL,0).

More generally, the channel Φ_(SEL,h) is selected by means of a radiocontrol transmitted by the station M_(h) by means of a service channelΦ_(CTRL,h), and typically on the channel Φ_(SEL,0) one receives bydefault the video camera F_(K) that generates the alarm by means of anexternal sensor or by means of image processing software and transmitsthe signal that arrives from the node F_(K) to all the other nodes.

The image received preferably from the mobile station is displayed witha PIP system on the image of one's own video camera, which is alwayspresent. This allows to never lose sight of what is in front of the userwho is operating in emergency conditions and to have additionalinformation displayed with the PIP system and accordingly superimposedon one's own image.

Furthermore, the PIP system can be used to display on a single displayboth the image that arrives from a video camera that operates in thevisible-light range and the image that arrives from a video camera thatoperates for example in the infrared range.

The surveillance system, as already mentioned, can be integrated in aUMTS system. In order to use a UMTS system, the transmission frequencyis comprised between 1885 MHz and 2025 MHz or 2110 MHz and 2200 MHz, anda CDMA access protocol is used for transmission and reception, eachterminal being identified by an identification code.

The advantages of the integration of the surveillance system in a UMTSsystem are that it is possible to manage the signal over a commercialnetwork that is expected to be widely available in the territory ofevery country and with efficient coverage, optionally with the aid ofsatellites.

Furthermore, integration allows to improve signal management in case ofoverlap of signals transmitted by adjacent nodes, increasing the numberof channels available for services and controls (selection of intendedchannel, sending of control signals, et cetera). Finally, integrationallows a user provided with a UMTS terminal to use the informationreceived from the surveillance system, allowing to identify escaperoutes in case of fire or disaster and to have communication messagesregarding the actions to be taken. By means of software managed by acontrol center, it is in fact possible to display an escape route or atleast indicate the location of fires or dangerous areas to be avoided.

With reference to FIG. 9, this use is applied for example in themonitoring of cars, subway or rail tunnels, where the smoke generated bya fire would prevent location of the accident and of the path to betaken to escape. In this case, the video cameras of the fixed stations(F_(1,j), F_(2,j), . . . ) located in the tunnel can transmit to a motorvehicle or to a person the pictures that are proximate to the point ofthe accident.

Likewise, if stations according to the invention, i.e., stationscomprising video cameras, display means and means fortransmission/reception as described above, are mounted on motorvehicles, a motor vehicle that is located in the vicinity of theaccident can send the pictures to the surveillance system, making themavailable to other motor vehicles, which can therefore avoid enteringthe danger zone. At the same time, the individual motor vehicles canreceive the pictures that arrive from the transmission system and takethe appropriate actions for independent rescue.

If the motor vehicle A is in the vicinity of the accident, the picturesare sent by the motor vehicle A to the surveillance system and madeavailable to other motor vehicles B_(i) that follow and can thus avoidentering the danger area. At the same time, the motor vehicles canreceive the pictures that arrive from the transmission system and takethe appropriate self-rescue actions.

Reception by the vehicle occurs from the nodes that correspond to theF_(K) fixed stations located along the road or in the tunnels, and thevideo signal that is transmitted is the signal of the most significantvideo camera, on the channel Φ_(SEL,0) on which it is possible totransmit messages or indicate escape routes together with the data ofwhere the video camera is located. If the most significant viewpoint isthe viewpoint of the vehicle A, the video signal transmitted on a radiochannel Φ_(A,1) of A is received by the vehicle B of the private user bymeans of the channel Φ_(SEL,0).

Preferably, only rescue vehicles can use additionally the entire rangeof channels made available by the surveillance system and an additionalchannel Φ_(CTRL,h) for selecting the chosen video signal among all thevideo signals that are present in the fiber-optics system.

Finally, it is possible to consider other variations that are not shownin the figures and allow to deal with other problems that can occur incase of an accident. If it is not possible to transmit pictures from onelocation where an operator is located to a node of a surveillancesystem, it is in fact possible to use vehicles or aircraft with anindependent navigation system capable of shuttling back and forth,storing pictures received from the operator and then reaching a locationwhere they can access by radio the surveillance system and moving backand forth between the two areas that are disconnected from the point ofview of communication.

Considering a robotized vehicle or another means provided with anavigation system that does not need to be remote-controlled but canmove autonomously in an assigned area and can therefore enter areas thatcannot be reached by a wireless or satellite or fiber-optics signal,said device takes a series of pictures of the location of interest,records them and then reaches a location that can be reached by radiosignals in order to allow the transfer of the recorded pictures.

Said unit can optionally provide support for a safety operator who canenter the critical area, where the accident has occurred, withappropriate precautions that protect his personal safety but once in thecritical area can no longer communicate with the outside wirelessly, forexample due to the presence of shielding walls such as those thatsurround a nuclear reactor or the walls of caves. In this case, therobotized unit can act as a means of communication between the operatorwho cannot communicate with the outside environment, by shuttling backand forth between the area in which the operator is located and the areain which it is possible to communicate with the surveillance system.

In the case of aircraft, it is possible to receive pictures from all theaircraft moving on the runway, in order to perfect alert systems in caseof incorrect operations. In particular, in the case of aircraft movingin an airport, it is possible to install on the airport runway codedheat sensors that locate and define their position. In this manner, thevideo cameras located on the aircraft can identify the position of theground references and can simultaneously receive the pictures and therespective position also referred to the other aircraft and movingvehicles, which is vitally important in case of poor visibility due forexample to fog.

Another application of the helmet is the implementation and use inhigh-risk centers (nuclear power stations, refineries, petrochemicalfacilities, centers with a high concentration of people such asstadiums, shopping centers or squares or wooded areas).

It has thus been shown that the helmet proposed allows to achieve theintended aim and objects.

The invention thus conceived is susceptible of numerous modificationsand variations, all of which are within the scope of the appendedclaims. All the details may further be replaced with technicallyequivalent elements.

The disclosures in Italian Patent Application No. MI2003A000121 fromwhich this application claims priority are incorporated herein byreference.

1. A helmet for displaying environmental images in criticalenvironments, comprising at least one video camera and means fordisplaying environmental images, further comprising a supportingstructure that can be anchored to said helmet in order to support saidat least one video camera and said display means, said supportingstructure comprising a front adapter that can be coupled to a front edgeof said helmet, a rear adapter that can be coupled to a rear edge ofsaid helmet, and a rigid connecting element for mutually connecting saidfront adapter and said rear adapter, further comprising a frame that ismounted detachably on said front adapter, said frame comprising meansfor supporting said video camera and means for supporting said displaymeans, wherein said frame comprises a bridge-like structure thatmutually connects elements for coupling to said front adapter, saidelements for coupling being arranged on opposite ends, of saidbridge-like structure, said bridge-like element extending from left toright, transversely with respect to said front adapter, said elementsfor coupling being arranged at left and right ends of said bridge-likeelement, said bridge-like element protruding from the front adapter soas to space said display means in front of the eyes of a person thatwears said helmet, said display means being rotatable upward to beplaced substantially in line with said front adapter, so as to pass froman operative position wherein the display means are arranged in front ofthe eyes of the person that wears the helmet to an inoperative positionwherein the display means are arranged in line with the front adapterand out of the line of sight of the person that wears the helmet.
 2. Thehelmet according to claim 1, wherein said means for supporting said atleast one video camera are fixed to said bridge-like structure andcomprise at least one mechanical connector for fixing said video camerato said supporting structure and a power supply connector for connectingsaid video camera to a power supply.
 3. The helmet according to claim 2,wherein said power supply comprises a battery that is mountedmonolithically with said rear adapter and comprises a cable for theconnection to said power supply connector of said supporting means. 4.The helmet according to claim 1, wherein said front adapter protrudeswith respect to said helmet substantially at right angles to the frontpart of said helmet, forming a peak, said peak comprising an edge andsaid coupling elements comprising hooks for coupling to said edge. 5.The helmet according to claim 4, wherein said hooks form a guide for thesliding insertion of said peak in said frame, said hooks having asubstantially straight longitudinal extension.
 6. The helmet accordingto claim 1, wherein said coupling elements comprise a respective pivoton which said display means are fixed so that they can rotate.
 7. Thehelmet according to claim 1, wherein said display means comprise atleast one display.
 8. The helmet according to claim 7, wherein saiddisplay comprises opposite side walls in which there is a respectiveguide, each pivot of said coupling elements being engaged with therespective guide of said side walls in order to allow a combined rotaryand translational motion of said display with respect to said helmet. 9.The helmet according to claim 1, wherein said front adapter and saidrear adapter comprise respective undercuts whose profile iscomplementary to said front edge and to said rear edge respectively. 10.The helmet according to claim 1, comprising means for radiocommunication of environmental images, said image communication meansbeing connected electronically to said at least one video camera and/orto said means for displaying environmental images, in order to transmitremotely environmental images acquired by said video camera and/ordisplay on said display means environmental images acquired by a remotevideo camera.
 11. The helmet according to claim 10, wherein said meansfor radio communication are mounted detachably on said rear adapter. 12.The helmet according to claim 1, comprising a PIP circuit forsimultaneously displaying images acquired by different video cameras onsaid display means.
 13. The helmet according to claim 12, wherein saidPIP circuit is mounted detachably on said rear adapter.
 14. The helmetaccording to claim 10, wherein said means for communicatingenvironmental images comprise at least one transmitter for transmittingby radio at least one video signal of a respective video camera over arespective communication channel and at least one receiver for receivingby radio at least one video signal on a second communication channel.15. The helmet according to claim 1, comprising means for deflecting theenvironmental image that are mounted upstream of said at least one videocamera, said deflection means comprising motorized means and a mirrorthat is mounted on said motorized means upstream of said at least onevideo camera in order to reflect the environmental image onto said atleast one video camera according to multiple angles and accordinglywiden the viewing field.
 16. The helmet according to claim 15, whereinsaid motorized means comprise a galvanometer in order to make saidmirror oscillate between two extreme positions, said environmental imagedeflection means furthermore comprising a shutter that is mountedbetween said mirror and said at least one video camera, in order toacquire the environmental image at said extreme positions.
 17. Thehelmet according to claim 15, further comprising stereoscopic visionmeans, said stereoscopic vision means and said image deflection meansbeing mounted on different planes, said stereoscopic vision meanscomprising two eyepieces, each eyepiece being coupled to a reflectingmeans that is orientated so as to reflect the environmental image ontosaid mirror mounted on said motorized means.
 18. The helmet according toclaim 1, wherein said display means comprise a display chosen from thegroup that comprises liquid-crystal displays and displays of the organiclight emission (OLED) type.
 19. The helmet according to claim 1,comprising a plurality of video cameras arranged along mutuallyperpendicular planes and selected from the group that comprises videocameras that operate in the spectral domain of visible opticalfrequencies, video cameras of the thermographic type that operate in theinfrared spectral domain, and video cameras with image intensifier,which operate in a spectral domain that comprises near-infrared opticalfrequencies.
 20. The helmet according to claim 19, comprising splitterlaminas in order to divide the acquired environmental images into theirvarious spectral components and direct them toward said plurality ofvideo cameras.
 21. The helmet according to claim 1, comprising means fordigital recording of the acquired environmental images, said recorderbeing mounted detachably on said rear adapter.